Does Israel’s New Polio Outbreak Threaten Global Eradication Efforts?

An expert sheds light on what polio virus found in the nations sewers means for the world

Image: iStockphoto/Thinkstock

Public health advocates have long set their sights on wiping out polio worldwide, but recent resurgences of the pernicious disease raise questions about its future eradication.

Several months ago a wild strain of the virus surfaced in a sewer system in Rahat in southern Israel, and now it has reportedly been detected throughout the country. Israels government this week launched a nationwide vaccination campaign, attempting to inoculate all children under nine years of age with oral polio vaccine (OPV), a form of the vaccine containing a live, weakened form of the virus. Most of these children were already vaccinated as babies with inactivated polio vaccine (IPV), otherwise known as the dead-virus vaccine. But people who were injected with IPV can still be healthy carriers of the disease and shed the virus in feces.

Scientific American spoke with Bruce Aylward, assistant director general for Polio, Emergencies and Country Collaboration at the World Health Organization, to find out more about the situation in Israel and how recent events there are affecting global efforts to wipe out the disease.

[An edited transcript of the interview follows.]

What is happening in Israel right now? What we know is that there is widespread detection of a wild polio virus at a number of sites that we have sampled, going back three-plus months. This virus is very similar to a strain that was detected in December of last year in Egypt, in the sewage there. This original virus came from Pakistan. Whether it went into Egypt and then Israel or Israel and then Egypt or [whether it spread via] two separate importationsit is unclear.

The virus has only been found in sewage at this point. There have not been any clinical cases of this so far; no children have been paralyzed. In the past [Israel] has detected [polio] virus from surrounding countries and it has disappeared very quickly, but this time it is persisting for longer. The virus cant live in the sewage itself and multiply. What we are seeing is persistence of [people excreting] the virus.

How high is Israel's vaccination coverage? This is a country with quite high immunization coverageabout 94 percentage of coverage. Its with the inactivated virus, the dead-vaccine virus that Dr. [Jonas] Salk made in the 1950s (versus the live vaccine coverage that [Albert] Sabin developed, which we mainly use in the vaccination program). Since the kids dont have intestinal immunity, or not very much, the disease is managing to spread.

The reason the oral vaccination is used in the vaccine campaign is it provides intestinal immunity that is so crucial in stopping the person-to-person transmission spread in settings where you might have a high transmission rate of the viruslike in tropical areas or areas with suboptimal sanitation. For a long time in developed countries Sabins vaccine was the vaccine of choice, but the drawback was one in a million times a child can get the disease and get paralyzed. Its very rare, but its a risk.

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Does Israel’s New Polio Outbreak Threaten Global Eradication Efforts?